This invention relates to a method for producing lined tanks, particularly water heater tanks which require lining as protection against corrosion. In particular, this invention relates to a method for installing flexible liners in metallic water heater tank shells having a welded construction.
1. Field of the Invention
The welding of lined tanks for water heaters has historically created problems due to the heat generated at the weld joint and conducted throughout the weld heat-affected zone. For example, welding of enamel lined water heater tanks sometimes generates heat sufficient to cause the enamel lining to crack. Similarly, welding a water heater tank that is provided with a polymeric coating generates heat causing the lining to melt, soften, or distort, especially at locations adjacent the weld joints. Accordingly, the integrity of conventional coatings and linings is compromised and, in some cases, utility is threatened or destroyed.
Co-pending application Ser. No. 08/195,387 discloses a new lined storage tank having a welded outer shell and a separate flexible liner mounted within the metal shell close to or contacting the shell inner surface. The liner is normally composed of polymeric or other low-melting but corrosion-resisting material and is provided as a vapor and liquid barrier to prevent corrosion of the shell. Accordingly, a method is required for producing a storage tank assembly of the type disclosed in the aforementioned co-pending application without destroying the integrity of the liner.
2. Objects of the Invention
It is an object of this invention to provide a method for producing a lined storage tank having a welded outer shell and a flexible low-melting liner.
It is another object of the invention to provide a method for producing a welded storage tank without damaging a liner positioned within the tank at or near a weld joint area.
It is a further object of the invention to provide a reliable, inexpensive, and efficient method for producing superior lined storage tanks.
It is yet another object of this invention to provide a method for producing novel corrosion-resisting tanks for water heaters.